Патент USA US2134896код для вставки
Now 1, 1938. B. n. H. TELLEGEN ET AL 2,134,396 ELECTRON DI SCZ‘IARGE EE'V'I Filed April 19, 1338 ’ BERNARDUS BY INVENTOR. D. H. TELLEGEN MARC ZIEGLER We - A TTORNEY. Patented Nov. 1, 1938 2,134,896 UNITED STATES PATENT OFFICE 2,134,896 ‘ELECTRON DISCHARGE DEVICE Bernardus Dominicus Hubertus Tellegen and Marc Ziegler, Eindhoven, Netherlands, assign ors to N. V. Philips’ Gloeilampenfabrieken, ‘Eindhoven, Netherlands Application April 19, 1938, Serial No. 202,820 In Germany March 17, 1937 3 Claims. (Cl. 250-275) This invention relates to electron discharge tube the invention permits the distribution hiss tubes to be used in a circuit arrangement for the factor to be made smaller than 1/8. we have ampli?cation or frequency transformation of found, however, that in frequency transformation electrical oscillations, in which at least the ?rst arrangements, wherein the incoming oscillations tube comprises two or more electrodes at a posi and the locally produced oscillations are supplied tive potential. to different grids in a mixing tube, this limit must As is well known, ‘biasing occurs in radio ar be given a higher value, that is a distribution hiss rangements from the coupling elements and from factor of l/2. the tubes and more particularly from those cou pling elements and tubes wherein the incoming ‘signal has only a small amplitude, for instance, in the high frequency part of a radio receiving arrangement. The principal object ‘of our invention is to pro The invention will be more clearly understood by reference to the following calculation. issuing entirely independently of each other from a hot cathode, is represented by the Well-known expression for the shot effect: ' vide an electron discharge device particularly suitable for ampli?cation or frequency transfor mation in which tube noise and hiss is reduced. The novel features which we believe to be char acteristic of our invention are set forth with par ) ticularity in the appended claims, but the inven tion itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a schematic diagram of an electron discharge device made according to our invention and Fig ure 21s a modi?cation of the electron discharge device shown in Figure 1 and employing our in vention. Extensive experiments indicate, especially in 5 connection with hissing caused in the tube, par ticularly when used at high frequencies, that by making use of an arrangement of an electron discharge device according to the present inven tion hissing can be substantially reduced. 3;, In a circuit arrangement for the ampli?cation or frequency transformation of electrical oscil lations wherein at least the ?rst tube comprises two or more electrodes having a positive poten tial, the distribution hiss factor of the currents 40 and voltages used in the apparatus is, according to the invention, made smaller than l/8. The fact that a screen grid tube involves more hissing than a triode was found to be due to accidental variations in the ratio between the v-a 5; screen grid current and the anode current. According to the invention the oscillations of the anode current in a screen grid tube are re U duced to a minimum by rendering ‘the screen grid current or the variations of the ratio between the screen grid current and the anode current to be as small as possible. > In an amplifying arrangement or in a frequency transformation arrangement, in which the incom ing oscillations and the locally produced oscilla "50 tions are supplied to the same grid of a mixing The i value of the oscillations of the stream of electrons 3:5 (1) wherein T2: the contribution from a definite frequency band to the average square variations of the emission; 17. average emission current; Cztwice the charge of the electron times the width of the frequency band in question. This formula holds good for the current varia tions of a saturated diode, in which all of the electrons issuing from the cathode pass to the anode. In cases wherein a potential minimum occurs due to the space‘ charge in the vicinity of the cathode, so that part of the electrons returns to the cathode, a certain regularity evolves in the stream of electrons leaving the space charge, so that the variations of this current are smaller than the pure accidental variations which are ex 35 pressed by the equation: ii=F?.C.I,, (2) wherein the “hiss factor” Fi is smaller than 1. Generally the hiss factor is to be understood to mean the ratio between the average square variations of a stream of electrons which pass en tirely independently of one another and which stream has a uniform value on an average. The regularity of the stream of electrons leav ing a space charge may ‘in practice be such that the hiss factor Pi is smaller than 0.05. In elec tron tubes, wherein the anode current forms only part of the total cathode current, the anode cur rent may relatively and absolutely carry more 50 variations than the cathode current due to the fact that the division of the total number of elec trons in anode electrons and remaining electrons is accidental to a certain extent which involves “distribution variations”. 2 2,134,898 current correspond to the sum of the independ ent contributions of Consequently the hiss factor Ff of the anode current Ia in cases, wherein the an ode current is smaller than the cathode current, Ta and E5 must be higher than the hiss factor Ff Thus we have, in accordance with (2): of the cathode current Ti=1-C-[FiZl+aI";-I“~C-[(1— all IT. 10 I: For a de?nite ratio between (4) Now, per de?nition: I“, 55:12.01‘; and so that R an upper limit of F2: z+[a%]c- a) F3 (s) k can be calculated by considering the electron 20 distribution as a pure calculation of probabilities. A calculation of probabilities shows that if the total current T, In an electron discharge tube having one or 20 more grids I,,—I,,=1, and (5) acquires the form: were perfectly uniform, F2: . I 2 -_~”_i+a Ia+1g< 1— i)2 < 6> ( i=0), the hiss factor of the anode current would be: 011L151 30 (3) lie the accident factor or being 1 if the distribution answers to pure accident laws, and smaller than 1 if the distribution takes place in conformity to certain geometrical laws. However, the stream of electrons In order to obtain a small value for F2 2 the two members of the right hand part of (6) 30 should be small. In the ?rst place the hiss factor of the cathode current, in the second place the factor H originating from the space charge is never per fectly uniform, so that 40 which will be called the distribution hiss factor According to (6) it has a value 40 However, this stream may be imagined to be split up in a, fraction TE=F§IY and can be determined experimentally for any 45 with complete accidental variation (hiss factor :1) and a fraction Ik0=(1—F:>Tk which is perfectly uniform (hiss factor=0). 50 The part of TH. going to the anode, which part amounts to E. 55 TfFkra has a hiss factor 1, because in view of the fact that initially complete irregularity prevails, no 60 greater disturbance can be brought into each part due to the distribution, whilst there is neither a mechanism providing regularity. The portion Z5 of 71.?) going, to the anode which portion has a value of 76f, k z: (1_ all‘ Ik has a hiss factor represented by (3), viz: aIkO—I,,O=aI,,fl,, 75 These considerations apply for an arbitrary number of positive grids in the tube. However, it was taken for granted that the grids had a constant voltage. When (in a mixing tube) one of the grids has an alternating voltage, whose frequency is not low in comparison with the fre quencies of the band transmitted on the anode side, the relations inferred no longer hold good. In contradistinction thereto it will be obvious that if for the whole cycle of adjustments tra versing the tube, the hiss factors, considered statically (for which case the formulae apply) 7.,_ 2 11,0 electron discharge tube. 1;, The total average square variations of the anode be as favorable as possible, the hiss factor of the tube during operation will also be as favorable as possible. Thus, the means for keeping the hiss factor of the anode current of a mixing tube as low as possible correspond to those referred to above. ' The invention has for its purpose to make the distribution hiss factor as small as possible and more particularly smaller than 1A; for am plifying arrangements and frequency trans formation arrangements, in which the received oscillations and the locally produced oscilla tions are supplied to the same grid of the ?rst detector tube, and smaller than 1A2 for frequency transformation arrangements in which the re ceived oscillation and the locally produced oscil lations are supplied to different grids of a mixing 76 3 2,134,896 tube. This can be ensured in various ways. Pri- with each other or extend in one plane. The screen grid 4’ forming part of the tube shown in marily the ratio In Figure 2 may consist of ?at ribbon wound as a 2+2 helix or may be of plate-shaped parts if the elec trodes are planar. The electrodes are preferably concentricate in which case grid 3’ may be wound as a double helical grid, that is the grid includes a in a screen grid tube may be made as small as possible, i. e. the screen grid current may be reduced to a minimum. In an arrangement ac“ cording to the invention an electron discharge 10 tube may be used for this purpose, the electrode system of which tube includes, among other elec trodes, a screen grid and in which tube the ac tive parts of the screen grid, seen in the direc tion from the cathode to the anode normally to the cathode surface, lie in the shadow of the active parts of one or more grids arranged be tween the cathode and the screen grid. According to a particular form of construction of the present invention the high frequency part 20 of a radio receiving arrangement comprises a tube having a control grid with variable pitch, and in which the screen grid arranged behind the con trol grid is Wound so as to be variable substan tially in the same manner as the control grid. 25 For solving the problem put with the invention it is not necessary to use grids wound with a var iable pitch, since it is also possible to use grids known arranged one behind the other and not wound with a variable pitch. 30 In frequency transformation arrangements in which the local oscillations and the received os cillations are supplied to two different grids in the mixing tube the active parts of all grids might be arranged in their respective shadows. However, 35 this has the objection that the control grid re motest from the cathode has an insu?icient con trol effect on the stream of electrons which may involve serious di?iculties more particularly when this grid is used as an input control grid. For this reason it is well-nigh impossible in. such a mixing tube to arrange all grids one behind the other, so that the distribution hiss factor is al ways larger than in a high frequency amplifying arrangement or in a frequency transformation arrangement, in which the local and received os 45 cillations are supplied to the same grid. Another method of making the distribution hiss factor as small as possible is to make the ac cident factor a as small as possible. This is achieved when each of the current conveying 50 electrodes receives its electrons from a different part of the space charge, which part is as inde pendent as possible. They may be e?ected by means of such a construction of the screen grid that the cathode can be imagined to consist of 55 two or more parts, substantially all the electrons emitted by one part passing to the anode. and substantially all of those emitted by another part 60 passing to the screen grid. For this purpose an electric discharge tube may be used whose elec trode system includes, inter alia, a screen grid and in which this screen grid consists of plate shaped parts. , Finally a combination of these two measures may be used. 65 In the drawing the envelope l of a tube en closes a cathode 2, a control grid 3, a screen grid 4 and an anode 5. As appears readily from the drawing the tube shown in Figure 1 is provided 70 with a control grid and a screen grid both of which are wound with a variable pitch and whose active parts, seen in a direction from the cathode to the anode normally to the cathode register pair of spaced interspersed helical wires wound in the same side rods. This permits positioning of the outer concentric ribbon grid so that its solid portion registers with alternate spaces be tween the turns of the wires and the space be tween the turns of the ribbon grid registers with other alternate spaces between the turns of the wire grid. If the wire grid comprises a plurality of parallel rings, the ribbon grid may comprise a plurality of parallel rings registering with al ternate spaces between the wire rings. The circuit associated with the tube shown in Figure 2 comprises an input circuit 6 connected between the cathode 2' and the control grid 3', and an output circuit 1 connected to the anode 5', the screen being biased by a proper connection to the source of voltage supply 8, While we have indicated the preferred embodi ments of our invention of which we are now 10 15 20 25 aware and have also indicated only one speci?c application for which our invention may be em ployed, it will be apparent that our invention is by no means limited to the exact forms illustrated 30 or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of our invention as set forth in the appended claims. 35 What we claim as new is: 1. An electron discharge device having an en velope containing a cathode and an anode and at least two grids between the cathode and an ode, the grid next to said cathode comprising 40 spaced wires and the grid closer to the anode comprising spaced ?at members of greater pro jected area than the Wire members of the grid next to the cathode, each of said ?at members registering with a space between two adjacent 45 wire members, and each of the spaces between the ?at members registering‘ with a space be tween two adjacent wire members. 2. An electron discharge device having an en velope containing a cathode and anode, at least two grids between the cathode and anode, the 50 grid closer to the cathode including a pair of spaced interspersed helical wires and the grid closer to the anode including a helical ribbon grid, the solid portions of the ribbon grid regis tering with the alternate spaces between the grid wires, and the space between the turns of the ribbon grid registering with the other alternate spaces between the grid wires. 3. An electron discharge device having an en 60 velope containing a cathode and anode, at least two grids between the cathode and anode, the grid closer to the cathode comprising a wire grid of a number of turns and the grid closer to the anode comprising a ribbon grid of a number of turns, each turn of the ribbon grid registering 65 with the alternate space between two adjacent grid wires and the spaces between the turns of the ribbon grid registering with the other alter nate spaces between two adjacent grid wires. 70 BERNARDUS DOMINICUS HUBERTUS TELLEGEN. MARC ZIEGLER.